Hot Rods Oil in coolant - Chevy 250

Ok, I'm pulling my hair out on this one, the 250 Chevy six (1972 N#v# ) in my 36 Chevy has been getting warmer than usual and there is a muddy milkshake going on in the radiator. Started with a compression test, all cylinders read 130- 134 pounds ( low due to being at 8500'), No coolant mixing in oil or trans fluid ( TH 350) , drained and checked. Ran 2 leak down tests today, No bubbles in coolant. No bubbles in coolant while engine is running either but oil droplets on the top of coolant in filler neck. Have any of you run across cracks in the block between the pressurized oil passages and the cooling system on Chevy sixes ? I feel it's not a cracked head as there is no pressurized oil passages on those, the only pressure is thru the pushrods. The engine had 60 plus thousand on it, I replaced the seals and gaskets, oil pump ,checked the bearings, had the head HOT tanked and lapped the valves, the cylinders look great with just a trace of a ridge. Its got a fair amount of leakdown past the rings but everything else looks good. I have been running this engine for the past 3 or 4 years, this just recently started while coming up the hill from Denver. Maybe its time for me to bite the bullet and build a new inline for the old gal, any ideas?? Thanks, Mitch.

 

Pressure test it and see if it is losing pressure

 

SD, That's the first thing I did, pumped it up to 14# and it slowly leaked down, very very slowly. Made sure the tester cap wasnt leaking. There wasn't even a trace amount of coolant in the oil. This one's got me scratch'in my noggin. Mitch

 

Well, I've been going round and round about building a proper hot rod inline, so I guess now's the time. This'll push the 25 Dodge build back even farther. Mitch.

 

Timing cover may be leaking coolant into the oil

 

drain the oil out,leave the drain plug out see if coolant comes out the drain plug after pressuring it for a while

 

Sdluck, just a question off the current topic, do you happen to know a guy named RICHARD that owns an antique shop in San Jose, he bought my 36 Ford Tudor. Great guy, got a great car, Just wondering. Mitch.

 

I've spent the last half hour going through the Leo Lantuci Chevrolet inline power manual and cannot find any place on the engine where the oil and water passages (oil under pressure) have a shared gasket.
The 250 doesn't have the plate on the front of the engine like the 216, 235 and 261 do. A leak behind that plate and a water passage was my second thought but no plate according to the Santucci book.
Pushrod oiling so there is no place for oil pressure to leak at the head gasket.

 

Block cracked in the lifter bores.

 

As the main oil galley is pretty much all of where oil is under pressure I'd say He is correct.

Sent from my VS988 using The H.A.M.B. mobile app

 

I took that one to a new height by taking a snaIt p of the page with my phone and posting from the phone. could be a pinhole in a thin area in the casting were it finally corroded through from the the inside of the cooling system rather than a crack.

 

I’d be double checking the trans cooler in the radiator. The trans cooling lines ‘probably’ carry more psi than the cooling system. That would permit oil (trans fluid) in the coolant but no water in the transmission.

Ray

 

Yes oldengine , I was thinking it might be a crack or "something" in the lifter area. Mr48s fancy photo phone work kinda gets me thinking more along those lines. RAY, if it was the cooler in the radiator, #1 I think the oil in the coolant would have a reddish hue instead of gand #2 after the engine is SHUT DOWN, the HOT coolant has more pressure than the trans so the coolant would be pushed into the cooler tube.( I think??) I'm going to pressure test that tomorrow and see what I can find. That would be an easier/cheaper fix than a new mill. Mitch.

 

I had an OT vehicle that "popped" the transcooler in the radiator & had the same problem & questions, but one thing puzzled me : no decrease in oil in the pan/ no water in the trans/ no water in the oil. Puzzled me until the pressure from the trans fluid rather spectacularly "blew" the tank off the radiator & revealed the problem! Changed the radiator, flushed the cooling system & trans lines : problem solved(although I still get some transfluid "blobs" coming out of the radiator from time to time)

 

Thanks drtrcrv8, gonna check the trans cooler tomorrow.

 

I had a 65 3/4 ton chev p/u that had a 250 in it.. Same scenario oil in the water.. Machine shop told me had cracked block, never over heated or anything just a mess in the rad. Drove several years that way until it got tired and yanked it to put in a big block.


EDIT: Never did get water in the oil..

 

After oil and water mix and you get that milkshake looking stuff sometimes you can't tell if it was originally brown or red.

 

Tanks guys, like the saying goes, " IF ITS GOT "B(.)(.)BS" OR WHEELS ITS GOING TO GIVE YOU TROUBLE". Mitch.

 

My first thought is a blown head gasket and I still think that's a real possibility.
Pull each plug and inspect. Look for one or two that are really clean.
One of these does not match the others.
That will be the offending cylinder.

It does not take much to make that milkshake. A idle or rev test in the garage or driveway will not replicate the stresses of driving.
Pulling the head will tell more, look for the washed cylinder. Also with the head pulled you may be able to tell or see the path where oil is pushed into the coolant via the head gasket.

Every Chevy I owned that did the milkshake thing was from a head gasket.

The flathead Ford that did sort of similar.....no milkshake but loss of coolant......gas smell in the coolant...would idle cool all day...5 minute drive blew all the coolant out.....That engine had a cracked cylinder.....no oil in the water.... no...water in the oil...the crack only opened up when the engine was under stress.

 

MITCH 36 : I believe the original quote (from the '80s swap meet T-shirts) was : "If it's got tits or tires, you're gonna have trouble"!!

 

Having spent considerable time fixing 194/230/250/292 sixes in a Chevrolet dealership in the 1960's-70's, I tend to go along with the theory of cracks in the block in the lifter bore area. There is an oil passage under pressure running lengthwise and also coolant passages in the same area. Never say the problem very often, but we did see it. Never seemed to be any event that caused it......most likely some casting flaw that finally reared it's ugly head.
Good luck......have fun.

 

The 250's have been known to crack between the water pump hole and the front driver side head bolt.. Not sure if that could cause the problem.

 

No oil under pressure there though. To push oil or trans fluid into the cooling system rather than get coolant into the crankcase or trans it means that it is happening while the the car is running and what ever is loosing fluid is under pressure.

 

just bypass the trans cooler in the rad temp with some hyd hose

 

You might be correct IF this were a 216/235/261, but the 194 thru 292 have zero oil passage from the block to the head. Only oil that ends up on the head comes through the pushrods via the lifters.

 

I had a truck once that did that. I also had a new motor for it waiting for the time to put it in. I just kept driving it and drained the mud from the radiator and refilled it every other day. it was not overheating and ran fine. mine was the head gaskit.

not recommending this, I just need to keep my post count up so I remain a "notable member"

 

What engine make and model was in your truck?

Ray

 

F1, I've pulled the plugs and all 6 look exactly the same, bore scoped cylinders also for tell tale signs and nothing there either. Yesterday it wouldn't start, No spark. Turns out the pertronix module took a shit ( must have left key on maybe) so I put the point distributor back in. Trans fluid was low, the pan gaskets leaking but Im going to check the cooler for leaks and bypass/ install a cooler if that's it. That would be a easy fix. Ill drive her till she croaks while i build another inline.

 

If the engine oil level is staying where it should I'd suspect the trans cooler.
That could be handled right now by putting on an auxiliary trans cooler in front of the radiator and bypassing the cooler in the radiator all together and just put a pair of inverted flare plugs in it.

 

Well I finally got around to fiddling around with the 36 today. Absolutely No coolant in trans fluid or engine oil. Ran psi test on radiator and it sits solid( leaked down before cause cap wasn’t on tight). Pressurized trans cooler in rad and its good. I guess it’s time to build a new inline to replace this tired old leaky geezer. Oh well, mo money mo money mo money, now to look for a cheap 250 to start with. Mitch.